This invention relates generally to improvements in pulverizers or mills and more particularly to a micronization pulverizer capable of pulverizing particles to be pulverized into fine particles of sizes in the range of from micron order to a size between 10 and 20 microns.
A typical pulverizer known heretofore comprises essentially a cylindrical casing with a vertical axis having a material inlet at its bottom and a product outlet at its top, a cylindrical stator supported on the inner wall surface of the casing or formed integrally therewith, a rotor disposed coaxially within the stator, a vertical rotating shaft rotatably supported by the casing and fixedly and coaxially supporting the rotor, and motive power means for driving the shaft and the rotor in rotation. The outer surface of the rotor and the inner surface of the stator are respectively provided with mutually confronting ridges interspersed with alternately interposed troughs, the ridges and troughs extending in the direction of the generatrices of the rotor and the stator and having rectangular shapes in cross section.
In the operation of the known pulverizer of the above described general construction, as the rotor is rotated at high speed and suction is applied to the product outlet, the particulate material to be pulverized is fed and swept into the material inlet by air aspirated by the suction and, as it is wafted upward between the rotor and the stator by the upward air stream, is pulverized by a number of pulverizing actions between the material and the rotor and the stator as described more fully hereinafter.
In this known pulverizer, a wide gap of the order of from 2 to 5 mm; or even more, is provided between the ridges of the rotor and those of the stator. Such a wide gap becomes the cause of such shortcomings as weak vortices in the troughs between the ridges, low probability of the particles being struck by the rotor, and small force with which the particles are struck by the rotor, all of which are causes of poor pulverization performance. Still another problem encountered in the prior pulverizer is that, because of the nature of the upward passage of the particles through the pulverization chamber between the rotor and the stator, some of the particles pass through the pulverization chamber without being satisfactorily pulverized. As a consequence, the product obtained comprises particles of sizes in a wide range with an average particle size of the order of 40 to 60 microns.